1. Field of the Invention
The present invention relates to deposition system and method for controlling surface temperature of wafer and thin-film grown on the wafer.
2. Description of Related Art
Metal-Organic Chemical Vapor Deposition (MOCVD) is a process to deposit semiconductor thin-film on a surface. A carrier gas carries reactant gases and/or precursor gases into a chamber with a wafer. A susceptor under the wafer heats the wafer with a particular manner, so that the reactant gases or precursor gases approaching the wafer are heated to an elevated temperature. The elevated temperature will initiate one or several chemical reactions of the reactant gases or precursor gases, which are turned into solid products and then deposited on the surface of the wafer.
The temperature control for the wafer is an important factor during the MOCVD process. U.S. Patent Application US2013/0343426 discloses a temperature control method and system for growing GaN based materials. It employs a non-contact pyrometer 70 sensitive to radiation in a first wavelength band and a second wavelength band, so as to respectively measure the temperature of the susceptor and the surface temperature of the wafer. In addition, a wafer temperature measurement device 80, for example, a short wavelength pyrometer or an absorption shift based device, sensitive to radiation in a particular wavelength band, is used to measure the thin-film temperature during the MOCVD process. The inventor of the present invention considers that the conventional method has a problem which needs to be solved. Particles may be deposited on the surface of the wafer during the depositing process, and they will weaken the light signal of the temperature measurement device. Therefore, the measured temperature of an object, e.g., a surface of wafer, may be less than the real temperature of the object. If the inaccurately measured temperature is used to a feedback control of the temperature of the object, a target temperature of the object will be set too high. As a result, the high temperature will decrease the yield and may damage the components within the reactor chamber.